10 Cloverfield Lane
Leslie arrived at the bunker just as Michelle was going to open the door to escape. She begged her to let her in, but Howard order Michelle to keep the door closed. Desperate and outwardly injured in some fashion, Leslie became more aggressive and demanded entry, eventually smashing her head against the glass. Leslie stumbled away from the doorway as Michelle and Howard retreated back into the bunker; her self-induced injury from hitting her head, combined with prior wounds possibly sustained from the aliens' toxic gas, led to her death.
After Michelle escaped from the bunker, she was attacked an alien scout. She took shelter in Howard's shed and retrieved Leslie's car keys from her corpse; after a brief skirmish with the scout and an alien patrol ship that had also noticed her, Michelle used Leslie's car to escape and drive to the nearest city.
The Cloverfield Paradox
Although Leslie had perished in 2016, she appeared as a news anchor in 2030, interviewing Mark Stambler, who was the brother of Howard Stambler and a scientist discussing the possible side effects of the titular paradox. The fact that Leslie is alive here indicates that Paradox takes place in an alternate dimension to Lane, or that the Leslie from a parallel dimension had by some means entered the Lane dimension and occupied the original's place.